MPs will investigate the effect that the most radical reforms to policing in 50 years will have on the future of the service, it was announced today.

The Home Affairs Select Committee will look at the impact of the introduction of directly-elected police and crime commissioners amid concerns over how the operational independence of chief constables will be maintained.

Keith Vaz, the committee's chairman, said: "The landscape of policing looks set to change considerably in the near future if plans to implement directly-elected individuals go ahead.

"The committee looks forward to questioning the relevant stakeholders on the impact this will have on policing in the 21st Century."

The inquiry will also look at the extent to which there will still be a need for national targets and at the role of police and crime panels, which will be brought in with the new commissioners to replace existing police authorities.

Earlier, Home Secretary Theresa May said there was a "democratic deficit" at the heart of the current policing model.

"Police authorities just don't work," she told superintendents at their annual conference in Cheshire.

"You know it and the public know it - well, in fact, the public don't know it because only 7% of them have ever even heard of police authorities.

"This just doesn't make sense. If something is broken, and everyone knows it's broken, then we should fix it. Even if it is hard, even if it will ruffle a few feathers, we need to sort it out."

Mrs May said the new commissioners "will have a mandate from the public to hold his or her chief constable and police force to account".

"They will ensure that the police focus on what local people want, not on what national politicians miles away and their civil servant advisers think they want," she said.

"And let me make absolutely clear: police and crime commissioners will in no way undermine the operational independence that you rightly hold so dear.

"They will not manage police forces and they will not be permitted to interfere in the day-to-day work of police officers."

The Home Secretary went on: "The current system comes at a cost, but achieves little. I am confident that directly-elected police and crime commissioners will deliver benefits we could never get from police authorities."